( i6 ) 
I. Exercife. 
II. A too plentiful Meal. 
III. Drunkennefs, or a too great Quantity of 
fermented Liquors, or of their diftilled SpU 
rits. 
IV. The whole Tribe of Narcotics , or Soporifics', 
of which Opium , and its feveral Preparations, 
are the chief. 
I. Exercife appears to wafte all the Fluids, and 
particularly the animal Spirits, the aftive Inftruments 
of all Motion j fo that the Remains are not fuflicient 
for the Exigencies of the natural and vital Functions; 
and alfo to fupply the Demands of voluntary Motion, 
and to aflift in Senfation, and the Operations of the 
Mind. 
And here it is proper to fhow how this Wafte ne* 
celfarily brings on Sleep in a healthy Perfon, and 
how the natural and vital Motions, and Functions of 
Digeftion, Refpiration, and Circulation, notwith- 
ftanding this Wafte, do neceffarily go on in Sleep, 
leading the Remains of the Spirits to their Affiftance, 
and making the Deficiency fall to the Share of the 
animal or voluntary Motions and Organs of Sen* 
fation. 
In order to Ihew this, let us obferve what is very 
obvious, that when any Mufcle is brought into Afti- 
on againft our Will by a fuperior Force, as when a 
ftronger Man bends or extends my Arm contrary to 
my Will or Inclination, the Benders orExtenfers of 
my Arm fwell and contraQ: in the fame manner, and 
the Afflux of the Blood and Spirits to the con trading 
Mufcles, 
